Skeleton system
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100 Terms
How do bones support the body
limb bones, vertebrae, jaw bones, and some bones support viscera
What are the 6 functions of the skeleton
support
protection
movement
electrolyte balance
acid-base balance
hematopoiesis
What does the skeleton protect
The CNS, heart, lungs, and other soft organs
How do bones contribute to movement
bones provide structures acted upon by muscles
How do bones help electrolyte balance
they store and release calcium and phosphate
How do bones help acid-base balance
bone salts buffer changes in acid-base levels
What is hematopoiesis
blood cell production in red bone marrow
What is bone (osseous tissue)
connective tissue with a matrix hardened by calcium and other materials
What tissue make up an individual bone
osseous, marrow, blood, hyaline cartilage, adipose, nervous and fibrous connective tissue
What are the 4 bone classifications by shape
flat
long
short
irregular
What are flat bones
thin, curved plates that protect soft organs
Give examples of flat bone
skull bones and ribs
What are long bones
bones longer than wide that are important for movement
Give examples of long bones
arm and leg bones
What are short bones
bones approximately equal in length and width
What do short bones do
they glide across one another
Give examples of short bones
wrist and ankle bones
What are irregular bones
bones that do not fit the other shape categories
Give examples of irregular bones
vertebrae and pelvic bones
What is compact bone
the dense outer shell covering the surface of all bones
What is spongy bone
cancellous bone found at long-bone ends and inside most other bones
Where is spongy bone found in long bones
at the ends of long bones
What is diaphysis
the shaft of a long bone
What is the medullary cavity
the marrow-filled cavity within the diaphysis
What are epiphyses
the enlarged ends of a long bone
What is articular cartilage
hyaline cartilage covering a joint surface
What are nutrient foramina
small holes in bone where vessels enter
What is the periosteum
the external sheath covering most of a bone
What is the outer layer of the periosteum
a fibrous layer made mainly of collagen
What are perforating (Sharpey’s) fibers
fibers that penetrate into the bone matrix
What is the inner layer of the periosteum
the inner osteogenic layer containing bone-forming cells
What is the endosteum
a thin tissue layer lining the marrow cavity
What cells are found in the endosteum
cells that dissolve osseous tissue and cells that deposit it
How is a flat bone constructed
two compact-bone layers enclosing a middle layer of spongy bone
What is dipole
the spongy middle layer of a flat bone
What does dipole do
it helps absorb shock
What are osteogenic cells
stem cells in the endosteum and inner periosteum
What are osteoblasts
bone-forming cells that produce organic matrix
What happens to osteoblast matrix
it hardens through mineral deposition
What are osteoclasts
bone-resorbing cells found on bone surfaces
What are osteocytes
former osteoblasts trapped in the matrix they deposited
what are lacunae
tiny cavities where osteocytes reside
What are canaliculi
small canals connecting lacunae
what do osteocytes do
maintain and regulate bone remodeling, shape, density
What is the bone matrix made of
about one-third organic material and two-thirds inorganic material by dry weight
What is osteoid
the organic bone matrix secreted by osteoblasts
What is osteoid composed of
collagen and carbohydrate-protein complexes
What does the organic matrix provide
tensile and flexible strength
What is the main inorganic bone material
hydroxyapatite, a crystallized calcium phosphate salt
What percentage of inorganic bone matter is hydroxyapatite
85%
What does inorganic bone matter provide
hardness and rigidity
What is an osteon
the structural and functional unit of compact bone
What surrounds the central canal of an osteon
concentric lamellae
What is the central (Haversian) canal
a longitudinal canal running through an osteon
What are perforating (Volkmann) canals
transverse or diagonal passages through compact bone
What is the structure of spongy bone
a lattice of bone covered with endosteum
What are spicules
silvers of bone in spongy bone
What are trabeculae
thin plates of bone forming the spongy-bone lattice
What fills spaces in spongy bone
red bone marrow
Does spongy bone contain many osteons
No, it has few osteon and no central canals
Why is spongy bone useful
it provides strength with minimal weight
What is bone marrow
Soft tissue occupying marrow cavities and spaces in spongy bone
What does red bone marrow do
produces blood cells
Where is red marrow found in infants
in all marrow spaces
Where is red marrow found in adults
axial skeleton and proximal humerus and femur
What is yellow bone marrow
fatty marrow in adults that does not produce blood
What is ossification
the formation of bone; also called osteogenesis
What are the 2 pathways of bone development
intramembranous ossification and endochondral ossification
What does intramembranous ossification produce
flat bones and specific features of irregular bones
What does intramembranous ossification do throughout life
thickens long bones
What is endochondral ossification
bone development using a cartilage model
What happens to epiphyses during childhood
they fill with spongy bone
Where does cartilage remain in growing long bones
articular cartilage and the epiphyseal plate
What is the epiphyseal plate
cartilage plate separating epiphyses from diaphysis during growth
What is the metaphysis
the transition zone between the epiphysis and diaphysis
What does the epiphyseal plate allow
increase in bone length through interstitial growth
How long does the epiphyseal plate remain active
through childhood and adolescence
When does the epiphyseal plate generally close
by the late teens to early 20s
What happens when the epiphyseal plate closes
bone can no longer grow in length
What is the epiphyseal line
an adult bony scar marking the former growth plate
What are the two directions bone grow
length and width
What is appositional growth
growth at the bone surface that increases diameter and thickness
What does the osteoblasts do during bone widening
inner periosteal osteoblasts deposit osteoid matrix
What does osteoclasts do during bone widening
endosteal osteoclasts enlarge the marrow cavity
What is mineral deposition
calcium, phosphate, and other ions are deposited into bone matrix
What is mineral resorption
dissolving bone and releasing mineral into the blood
Which cells carry out mineral resorption
osteoclasts
What is bone remodeling
continuous bone resorption and deposition throughout life
What are 3 functions of bone remodeling
repairs microfractures
releases minerals
reshapes bones
What is Wolff’s law
bone architecture is determined by mechanical stresses placed on it
Why is calcium important in the body
for nerve function, muscle contraction, blood clotting
Where is calcium stored
in the skeleton, where it can withdrawn when needed
What is hypocalcemia
a deficient level of calcium in the blood
What can hypocalcemia cause
an overly excitable nervous system and tetany
What is hypercalcemia
an excessive level of calcium in the blood
What can hypercalcemia cause
reduced nerve and muscle excitability, weakness, and potentially cardiac arrest
What hormone lowers blood calcium
calcitonin, secreted by the thyroid gland
How does calcitonin lower blood calcium
it stimulates calcium deposition in bone
What hormone raises blood calcium
parathyroid hormone (PTH)
Where is PTH produced
by the parathyroid glands